We propose to study protein folding intermediates at two levels: (a) under suitable equilibrium conditions where we can stabilize partially folded states of proteins and (b) by direct kinetic measurements using stopped-flow time-resolved SAXS. SAXS data yield overall size and shape indication of the conformational state of a protein. High-quality, high-angle scattering profiles for cytochrome c have been measured at varying denaturant concentrations. We will use the combination of singular value decomposition analysis and a denaturant binding model to determine whether an equilibrium intermediate state exists. This analysis follows the method used to distinguish a folding intermediate for lysozyme (Chen, J. Mol. Biol. 261, 658-671). The A-states, partially folded intermediate states obtained at low pH with the addition of salt, of apomyoglobin have been characterized with SAXS. The apomyoglobin A-states stabilized with TFA, TCA, and KCl demonstrated different degrees of compaction, suggesting that there is not a unique A-state.